With agricultural harvesters, the throughput depends, proportionally, on the individual driving speed of the harvester. In order to use the harvester to capacity in the best way possible and to effectively utilize it, systems are known that automatically set the driving speed in the sense of maintenance of a desired crop throughput and to relieve the operator of the task of speed specification.
The density of the crops can vary with greater or lesser intensity on a field, which results in corresponding changes of the driving speed. The recording of the density, in particular, if it takes place on board the harvester by means of a throughput sensor (see, for example, DE 1 199 039 B), and the speed adaptation subsequent to a density change, require, however, a certain reaction time, which leads to a situation where the speed can be adapted to a change of the density of the crops on the field with only a temporary deceleration. This is particularly critical if the density suddenly undergoes a great increase, since then an overloading or clogging of the harvester may even result.
In the state of the art, solutions have been proposed in which the density of the crops on the field or a value dependent thereon is predictively determined and the driving speed specification is derived therefrom in such a manner that the harvester travels already at a suitable speed upon reaching a certain point of the field, whether by means of a card produced with a prior harvesting operation (DE 44 31 824 C1) or by means of a predictively operating sensor for the recording of the planting density (DE 101 30 665 A1). These solutions, however, have the disadvantage that more or less intense accelerations of the harvester continuously occur which, in any case, make themselves noticeable to the driver as strenuous and uncomfortable after long workdays.
A limitation of the available acceleration of a harvester for the purpose of improving the control of the operator is in fact known, in that the adjustment speed of an actuator defining the driving speed is hydraulically limited (DE 10 2006 037 631 A1), but a use of such a limitation with a predictively speed-controlled harvester would again lead to the problem that the crop throughput does not always agree with the theoretical value. In particular, the case can occur that with a sudden greatly increasing crop density, a sufficiently strong deceleration does not occur, so that the harvester is clogged or overloaded.